The overarching theme of this proposal is the application of new photoredox catalysis methods to the preparation of biologically active compounds. These methodologies provide strategy-level advantages in their respective syntheses due to broad functional group compatibility and mild reaction conditions. Importantly they will also enable syntheses in an environmentally conscious fashion. New methods using visible light, a non-toxic 'reagent' that does not generate chemical waste, are attractive strategies for chemical synthesis. Since most organic molecules do not productively absorb visible light, photosensitive catalysts, widely studied for their photophysical properties, have been successfully employed for numerous new chemical methods which will be applied in the synthesis of biologically active natural compounds. The compounds prepared as part of this proposal will be evaluated for their biological activity by the Inglese Laboratory at the NIH Chemical Genomics Center (NCGC) using their high throughput screening capabilities. Leads which arise from these screening activities will be followed up in collaboration with the medicinal chemistry group at NCGC. The initial targeted libraries will be prepared at BU, with follow-up scaffold development, where appropriate, using scaffolds prepared in the Principal Investigator's lab for modification at NCGC. In addition, the Liu Group (University of Colorado) will evaluate the effect of the developed compounds on cell-cycle regulation. The aims of the proposed research projects are to: 1) Synthesize the bisindole alkaloid natural products gliocladin C, deoxyleptosin D, deoxybionectin A and plectosphaeroic acid A, achieve the synthesis of heterodimeric bis(pyrroloindoline) alkaloids asperdimin and WIN 64745, undertake the syntheses of a series of indolizidine alkaloids using photoredox- mediated, stereocontrolled radical cyclization onto pyrroles, and achieve the synthesis of actinophyllic acid using a photoredox-catalyzed fragment coupling strategy. 2) Develop new methods for the ?-C-H functionalization of amines using photoredox catalysis and appyl these methods to the syntheses of the alkaloid natural products crispine A, harmicine, tangutorine and undulifoline.